runtime: fractional worker preemption causes performance degradation for single cpu #22693
Labels
compiler/runtime
Issues related to the Go compiler and/or runtime.
NeedsInvestigation
Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Performance
Milestone
What version of Go are you using (go version)?
What operating system and processor architecture are you using (go env)?
/proc/cpuinfo:
model name : Intel(R) Xeon(R) CPU E5-2609 v3 @ 1.90GHz
What did you do?
I've compared performance of 1.9 vs trunk on builtin benchmarks with -cpu=1 and found that some of them have regressed. Changes in performance were bisected to 28e1a8e which caused:
cmd/compile/internal/ssa/Fuse/10000 33.2ms ± 2% 38.1ms ± 2% +14.62%
text/template/parse/ParseLarge 43.2ms ± 1% 49.1ms ± 2% +13.60% (p=0.000 n=8+8)
This is reproducible only with go test -cpu=1 -bench=......
I doubt that -cpu=1 case is important, but CL message didn't mention performance impact, so I'm opening this.
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